Lymphomas represent about 4% of the new cases of cancer diagnosed in the United States each year, making them the fifth most common cancer diagnosis and a leading cause of cancer death. About 60,000 individuals are diagnosed with lymphoma every year, of which about 90% are Non-Hodgkin Lymphomas (NHLs), with the remainder being Hodgkin Lymphoma (HL). In fact, while the incidence of most cancers is decreasing, lymphoma is one of only two tumors increasing in frequency, although the cause for this increase is unknown.
Non-Hodgkin lymphomas are a heterogeneous group of disorders involving malignant monoclonal proliferation of lymphoid cells in lymphoreticular sites, including lymph nodes, bone marrow, the spleen, the liver, and the gastrointestinal tract. Presenting symptoms usually include peripheral lymphadenopathy. Compared with Hodgkin lymphoma, there is a greater likelihood of disseminated disease at the time of diagnosis. However, NHL is not one disease but rather a category of lymphocyte malignancies. These types can be divided into aggressive (fast-growing) and indolent (slow-growing) types, and they can be formed from either B-cells or T-cells. B-cell non-Hodgkin lymphomas include Burkitt lymphoma, chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), diffuse large B-cell lymphoma, follicular lymphoma, precursor B-lymphoblastic lymphoma, and mantle cell lymphoma, among others. T-cell non-Hodgkin lymphomas include mycosis fungoides, anaplastic large cell lymphoma, and precursor T-lymphoblastic lymphoma. Lymphomas that occur after bone marrow or stem cell transplantation are usually B-cell non-Hodgkin lymphomas. Prognosis and treatment depend on the stage and type of disease.
Although NHL usually respond initially to low dose chemotherapy and/or radiotherapy, relapses and treatment refraction occur after a period of months or years. Very high dose chemotherapy and/or radiotherapy with hematopoietic stem cell transplantation can induce longer remissions but unfortunately is substantially toxic, carries a high early mortality, and is not curative.
In B-cell lymphoma malignancies, a clonotypic surface immunoglobulin (Ig) expressed by malignant B-cells is known as an idiotype (Id) epitope. Id is a tumor-specific antigen and, therefore, provides a unique opportunity to target the tumor through a method of active immunotherapy, where the patient is vaccinated against the tumor-specific idiotype. Id proteins contain structures that can be recognized by antibodies and by CD4+ and CD8+ T cells and can be isolated from autologous tumor cells and formulated into a custom-made therapeutic tumor vaccine. A traditional approach for generating patient-specific Id vaccines involves fusion of individual patient's lymphoma cells with myeloma cells, yielding a ‘rescue’ hybridoma secreting large quantities of Id protein. The Id is then chemically conjugated to the highly immunogenic carrier protein keyhole limpet hemocyanin (KLH) rendering it more immunogenic. The resulting Id-KLH conjugate is then injected subcutaneously (s.c.) along with an immunologic adjuvant to evoke tumor-specific antibody and T cell responses.
Results from early clinical trials of Id immunization for follicular lymphoma using hybridoma-derived Id have included the induction of tumor-specific anti-Id immune responses that correlate with improved disease-free and overall survival, achievement of molecular complete remissions (bcl-2 negative PCR status) and favorable progression-free survival (PFS) using Id-KLH plus GM-CSF, and durable tumor regressions following immunization with Id protein-loaded autologous dendritic cells. However, limitations of the rescue hybridoma method include a production failure rate as high as 15%, the need for viable tumor cells for cell fusion, non-uniformity of the Id product (IgG, IgM or other isotype expressed by the tumor) and the instability of Id secretion by tumor hybridomas over time.
An alternative technique, ‘molecular rescue’, employs PCR amplification of the tumor-specific variable region Ig sequences from small numbers of tumor cells (107) for cloning into expression vectors carrying the desired immunoglobulin isotype backbone. This molecular approach obviates the need for surgical biopsy, as adequate material can be obtained by fine or core needle biopsy, bone marrow biopsy, involved peripheral blood or fluid collection aspiration. Phase I/II and III clinical trials have been performed with patient-specific therapeutic Id vaccines in patients with follicular NHL in first remission following chemotherapy.
However, significant variations in patient responsiveness have been found with anti-idiotype treatment, making it difficult to determine the optimal treatment for an individual. Although analysis of a pre-specified endpoint in the clinical trial data for personalized immunotherapy arm showed a highly statistically significant difference in the progression-free survival between patients who mounted a positive humoral immune response to the tumor-specific target and those who did not, there has not been a means of determining prior to therapy which patients will generate such serological responses. The present invention addresses the need for improved prognosis of patient responsiveness.